Pathogenic organisms such as nematodes, wire worms, cut worms, fungal and bacterial pathogens residing in soils cause major economic damage to crops that are grown in such pathogen-infested soils. At present, these pathogens are controlled by chemical pesticides. However, chemical pesticides are quite hazardous to farmers and the environment and will be phased out of use in the coming decade by anticipated regulations.
Soils in greenhouses have been sterilized by pipes buried under the soil which are conduits for heated water or steam piped through these buried pipes. This technology cannot be used in open fields, where it is economically impossible to bury acres and acres of pipes.
Soils differ in their physical makeup. Soils are classified as clay, clay loam, loam, and sandy. All of these types of soils are encountered in agricultural production. These soils, however, sandy, tend to form clods and these clods can be of varying sizes. Such clods, especially from clayey soils, can be as hard as stone. The pathogen's eggs, larvae and adults are normally inside these clods. When hot water or steam is used to sterilize the different varieties of soils, the hot water or heat generated by the hot water or steam does not get to the pathogens located inside the clods. Therefore only a partial kill of the organisms is achieved.
Attempts have been made to use steam and super heated steam to sterilize soil. However, in practice, this system does not work as the steam escapes through fissures in the soil into the atmosphere and is quite ineffective. The present invention is directed to the preparation of the soil to be sterilized and thereafter sterilizing the soil with hot water under pressure.